The present invention relates to a method of using integrated video and spatial position information to maintain and expand information located in a geographic information system. The method includes the high speed collection of video and spatial position data as well as fast and efficient storage of the data. Such a method is of particular use in updating the United States Census Bureau TIGER/Line.TM. files to improve the accuracy of coordinates contained therein, add missing street and address information, and add vehicle routing data. The method may also be used to create files similar to TIGER/Line files in areas where such files do not already exist.
The TIGER/Line files are a computer readable geographic database for the United States. The original sources of the database include U.S. geological survey maps, the 1980 U.S. Census Bureau DIME files, and various other sources. While these geographic files are usable as a base for a geographic information system, they are not recommended for detailed applications which require a high degree of positional accuracy. This is because the positional accuracy of the information contained in the file is limited by the scale of the U.S. Geological Survey maps from which the files are created.
In addition, information in the TIGER/Line files is only as complete and accurate as the source documents used by the U.S. Census Bureau and errors often occur in the compilation and translation of information from source documents. Further, the information is only as current as the year in which the source documents were compiled and translated.
Because the information contained in a geographic information system such as the TIGER/Line files must be continually updated to reflect the most recent changes in the information contained therein, it is desirable to provide a method for collecting and processing video and spatial position information in a manner that allows updated attribute information to be tied to previously obtained spatial positional information.
One way in which to acquire accurate spatial position information is through the use of the Global Positioning System (GPS). The Global Positioning System is a network of satellites which constantly transmits its location at known, precise times. Since the orbital position of each satellite is known, a GPS receiver on the surface of the earth can accurately measure the time it takes for the transmitted signal to reach the receiver's location on earth. This measurement provides the distance between the satellite and the receiver. To obtain three dimensional positioning, the GPS receiver takes this measurement from each of at least four orbiting satellites. Using geometric principles, the information gathered by the GPS receiver can be used to calculate the distance of each satellite with respect to the receiver and thus calculate an accurate spatial position on earth.
While the Global Positioning System can provide accurate spatial position information, problems arise when the GPS receiver is not able to receive information from at least four orbiting satellites. This occurs when the GPS receiver is obstructed by geographic features such as canyons or bluffs as well as by man-made structures. Problems also arise when a signal transmitted by an orbiting satellite is reflected from a nearby object, giving the GPS receiver one or more incorrect readings from that satellite.
A further problem with the use of the Global Positioning System to provide spatial position information is that spatial position readings are often provided by the GPS receiver at a relatively slow rate.